In mobile communications, it is required to set the radiation coverage of a base-station transceiver system (BTS). The propagation loss is an important issue in the future mmW 5G applications. Therefore, directional beams with high-gain are required to compensate the energy loss. However, the beamwidth of a directional beam is too narrow to provide sufficient coverage. Beam steering or multi-beam coverage is therefore required in the applications, where traditional approaches employ phased array of antennas. Especially for the multiple directional beam radiations, conventional approach requires to use multiple sets of phased array of antennas.